Field
This application generally relates to power production and waste processing. More specifically, it relates to systems and methods for extracting heat energy from compostable material and converting this energy to electricity with the aid of an updraft tower.
Background Art
One of the major problems facing the United States, indeed the world, is that of landfill pollution and inefficient waste processing. Every year the United States alone produces hundreds of millions of tons of municipal solid waste. Much of this waste is not recycled or composted. Of the portion that is composted, the heat energy generated by the composting process is almost never utilized. Additionally, locating potential landfill sites poses a significant problem as well. Landfills may contaminate ground water or cause other environmental and hazards and undesired aesthetic concerns.
Moreover, a chief concern facing the planet is finding alternative, renewable energy sources to replace conventional power plants that burn fossil fuels. Fossil fuel burning power plants, such as coal or oil burning plants, produce a host of unwanted greenhouses gases, which are believed to be a major contributor of global warming.
U.S. Pat. No. 4,275,309 describes a system for converting solar heat into electrical energy. The system has a collector region where large volumes of air are heated by the sun. This heated air then flows at a high speed towards the center of the structure due to a large pressure differential caused by a tall chimney-like tower that extends upward from the base of the structure. The high speed air drives a turbine that generates electricity. In the art, such systems are also known as a solar updraft towers. However, solar updraft towers in the prior art heat the air in their collector region with only solar energy.
Composting is the purposeful biodegradation of organic matter, such as yard and food waste, performed by micro-organisms, such as bacteria, yeasts and fungi. The microorganisms consume the organic, carbon containing matter and break it down into its simplest parts. This produces a fiber-rich, carbon-containing humus with inorganic nutrients like nitrogen, phosphorus and potassium that can be used as fertilizer, potting soil, or for other important agricultural purposes. Through aerobic respiration microorganisms use oxygen and water to break the matter down. This process generates heat. Temperatures within compost piles can rise as high as 100 to 150 degrees Fahrenheit. Many commercial composting facilities do not harvest or otherwise use the ample heat energy released during the composting process, and allow it to dissipate into the surrounding environment.
U.S. Pat. No. 7,956,487, which was issued to the inventor of the present application, describes a compost updraft tower that harnesses the heat energy produced during the composting process and converts that heat energy into electricity through the use of an updraft tower. Despite being groundbreaking at its time, many major developments and improvements to such compost updraft towers have been made by the present applicant since that time.
The aforementioned developments, which are described in greater detail below, significantly increase the efficiency and operability of the compost updraft tower, and also decrease production costs. Thus, there is a need for improved methods and systems for generating electricity from heat energy released during the composting process and the contents of the present patent application address those needs.